Automatic firearm



March 1, 1966 J. G. NEFF AUTOMATIC FIREARM 2 Sheets-Sheet 1 N Filed Aug. 7, 1964 INVENTOR.

Wham, 86mm 4" W2 James Greeorr Neff mw QQ mm mm March 1, 1966 J. G. NEFF AUTOMATIC FIREARM Filed Aug. 7, 1964 8mm $4M 2 Sheets-Sheet 2 INVENTOR. James Greeorv Nef f,

ATTORNEYS,

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3,237,522 Patented Mar. ll, 1966 3,237,522 AUTOMATIC ARM James Gregory Neff, 4162 Sherel Lane, Cincinnati, Ohio Filed Aug. 7, 1964, Ser. No. 388,053 8 Claims. (Cl. 89-182) in accordance with what is known in the art as the blowback principle. Under this principle, the gun is provided with a bolt which is free to slide back and forth on an axis parallel to that of the gun barrel. Such a gun is further provided with a powerful recoil spring tending to urge the bolt to the forward position.

The operation of such a gun is as follows. To prepare the gun to fire, the bolt is drawn rearwardly against the force of the recoil spring by some form of retracting handle. The bolt is retained in a rearward position against the force of the recoil spring by a scar which is operatively connected to the trigger. the submachine gun is ready to fire.

When the trigger of such a weapon is squeezed, the sear is withdrawn from engagement with the bolt, and the bolt is caused to move forwardly under the influence of the recoil spring. As the bolt moves forwardly, it strips a round of ammunition from the magazine and forces it into the chamber or breech of the submachine gun. The forward face of the bolt is provided with a fixed firing pin, and when the bolt slams home on the base of the chambered cartridge, the fixed firing pin strikes the primer of the cartridge, firing it. The force of the explosion in the chamber of the submachine gun simultaneously forces the bullet out through the barrel, and forces the bolt to the rear, compressing the recoil spring. During its rearward movement, the bolt (with the aid of an extractor and an ejector) automatically extracts and ejects the empty cartridge from the weapon. The bolt is finally stopped in its rearward movement by the recoil spring, which then drives the bolt forwardly repeating another cycle unless the trigger is released and the bolt is held in its retracted position by the sear. Thus, as long as the trigger is depressed, the bolt will continue to feed a new round into the chamber, fire it, and extract and eject the empty cart-ridge case until either the magazine is emptied or the trigger is released. Most submachine guns of the type described will fire at a rate of from 400 to 700 rounds per minute.

In a submachine gun of the type described, limited to firing only one type of cartridge, the cyclic rate of fire of the gun is inextricably related to the mass of the bolt. The action of forcing the bullet out through the barrel by virtue of the explosive force of the propellant has an equal and opposite reaction, namely that of forcing the bolt to the rear. The acceleration of the bolt rearwardly is inversely proportional to its mass, and directly proportional to the force exerted. The acceleration of the bullet forwardly is inversely proportional to its mass and directly proportional to the force exerted. Since the same force is exerted on both the bolt and the bullet (discounting friction), and since the bolt is of much greater mass than the bullet, it follows that the rearward velocity of the bolt will be much smaller than the forward velocity of the bullet at the instant when the force ceases to exist (i.e. when the bullet has left In this condition,

' located below the port on the barrel.

the barrel and the empty cartridge case has been forced from the breech end of the barrel, venting the explosive forces to the outside of the weapon).

The rearward movement of the bolt is used to compress the recoil spring to store energy for the next firing cycle. It will be understood by one skilled in the art that the smaller the mass of the bolt, the higher will be its rearward velocity, and the more powerful must be the recoil spring in order to check its rearward movement within a reasonable distance. On the other hand, the more powerful the recoil spring, the faster it will drive the bolt forwardly on the next firing cycle. Thus, the smaller the mass of the bolt and the more powerful the recoil spring needed to check its rearward movement, the higher will be the cyclic rate of fire of the weapon.

There are two characteristics which are of utmost importance for a submachine gun or other automatic weapon. The first, is a cycle rate of fire which is not too high (usually between 600 to 700 rounds per minute is desired). When the cyclic rate of fire is too high, the individual soldier is required to carry excessive amounts of ammunition which slows him down and hampers his movements. Furthermore, too high a cyclic rate of fire renders it diflicult if not impossible to control the weapon during firing, and its accuracy is decreased. The second characteristic relates to the weight of the weapon. The weapon should be sufficiently light to be easily manipulated.

In general, one of the heavier individual parts of a submachine gun is the bolt (usually averaging about 2 pounds). However, any attempt to reduce the weight of the bolt results in an increased cyclic rate of fire. Thus, in a weapon operating by the blowback principle, these two characteristics of weight and controlled cyclic rate of fire are diametrically opposed.

Heretofore, there have been numerous attempts to overcome this difliculty in automatic weapons. An obvious approach to the difficulty is the provision of a locking bolt (i.e. a bolt which cannot be forced rearwardly by the explosive pressure in the chamber at the instant of firing). By causing the bolt to lock at the instant of firing, and thereby delaying its rearward movement, a bolt of reduced mass may be used, resulting in a lighter weapon.

In automatic weapons having locking bolts, the most usual method of rel-easing the bolt is through the use of a gas piston. In such gas operated Weapons, a small hole is bored through the barrel near the muzzle. This hole serves as a port through which the high pressure gases behind the bullet pass and actuate a gas piston This piston unlocks and retracts the bolt in one motion by means of linkage between the gas piston and the bolt.

By means of a locking bolt, and a gas operated unlocking mechanism, the weight of such a weapon may be reduced, and its cyclic rate of fire controlled. However, such weapons are expensive to manufacture due to the close tolerances needed in the gas piston and cylinder, and the complexity of the parts required. Also, the mechanism of such weapons may be easily fouled should the weapon become dirty under combat conditions.

Other semi-locking mechanisms or delaying mechanisms have been utilized to overcome the above de scribed difficulties. However, such mechanisms often fail to reduce the overall weight of the weapon or fail to sufficiently control the cyclic rate of fire. Furthermore, such mechanisms are complex, expensive to manufacture and often easily fouled in combat conditions.

It is therefore a primary object of the present invention to provide an automatic weapon which is both light in weight and provided with a properly controlled cyclic rate of fire.

It is an object of the present invention to provide a weapon having a light weight locking type bolt, which is simple in construction and easy and inexpensive to manufacture.

It is an object of the present invention to provide such a weapon having a light weight locking type bolt and a properly limited cyclic rate of fire.

It is an object of the present invention to provide means for unblocking such a bolt, the unblocking means being simple in structure and not easily subject to jamming or the like from dirt or other factors encountered under combat conditions.

It is an object of the present invention to provide such a weapon having a bolt which locks to the barrel.

It is an object of the present invention to provide such a weapon having a bolt with locking means and a weight sliding on the bolt, and acting to unlock the bolt.

These and other objects of the invention which will be described hereinafter or will be apparent to one skilled in the art upon reading these specifications, are accomplished by that structure and arrangement of parts of which an exemplary embodiment will now be described. Reference is made to the drawings wherein:

FIGURE 1 is a simplified partial elevational view with the receiver in cross section, illustrating the structure of the present invention.

FIGURE 2 is a simplified partial top view with the receiver in cross section.

FIGURE 3 is a perspective view of a locking means of the present invention.

FIGURE 4 is a partial plan view of the barrel of the present invention.

FIGURES 5 and 6 are respectively elevational and planed views of the bolt of the present invention.

FIGURE 7 is an end elevation of the bolt of the present invention as seen from the left in FIGURE 5.

FIGURE 8 is a sectional View taken along the section line S8 of FIGURE 9.

FIGURE 9 is a partial cross sectional view of the bolt of the present invention, taken along the section 99 of FIGURE 8.

Briefly, the weapon of the present invention comprises a receiver and a barrel affixed thereto, one end of said barrel extending into said receiver. The weapon is also provided with a light weight bolt adapted to telescope on that end of the barrel which extends into the receiver, and is provided with means for looking the bolt on the barrel at the time of firing. A momentum actuated unlocking means is slidably mounted on the bolt, for unlocking the bolt at that instant when the initial high chamber pressure has subsided, but enough chamber pressure remains to blow the bolt to the rear against the force of a recoil spring. The momentary locking of the bolt to the barrel enables the use of a lighter bolt, insures that a lower velocity will be imparted to the bolt, and permits the use of a lighter recoil spring resulting in an easily controllable cyclic rate of fire.

Referring first to FIGURES 1 and 2, a submachine gun made in accordance with the teachings of the present invention will have a receiver 1 comprising a hollow cylindrical member having a closed end 2, and an open end 3. A barrel 4 may be affixed to the open end 3 of the receiver by any suitable means. As illustrated, the barrel 4 is provided with a mounting collar 5. For purposes of an exemplary showing, the mounting collar 5 comprises a conical portion 5a and a threaded portion 5b of reduced diameter. The open end 3 of the receiver may be provided with internal threads 3a for engagement by the threaded portion 512 of the mounting collar. The mounting collar 5 may be affixed to the barrel 4 by any suitable means. trated, a pin 6 is used.

As will be noted from FIGS. 1 and 2, that portion of the barrel 4 which projects rearwardly of the threaded part 5b of the mounting collar is adapted to extend within the receiver. This portion of the barrel is provided with a section 4a of increased diameter. As shown in FIG. 4, the section 4a of the barrel provided a shoulder 4b and has two diametrically opposed, longitudinally extending slots, one of which is shown at 7. The shoulder 41) and the slots 7 will be more fully described hereinafter.

FIGS. 5 through 9 illustrate the bolt 8 of the present invention. The bolt 8 comprises a central hollow cylindrical portion 9. The rear end of the cylindrical portion 9 is closed as at 10, providing the recessed face 11 of the bolt and a fixed firing pin 12. The closed end 10 of the bolt has a bore 13 within which an L- shaped extractor 14 is pivotally mounted as at 15. The short l-eg 14a of the L-shaped extractor is adapted to depend downwardly in front of the face 11 of the bolt to engage the rim of a cartridge for purposes of extraction as will be more fully described hereinafter. A radial bore 16 in the closed end 16 of the bolt comrnunicates with the bore 13 and is adapted to house a spring 17 which tends to urge the extractor 14 in the downwardmost position. The closed end 10 is provided with a removable collar 18 which serves not only to retain the spring 17 but also to enlarge the rear end of the bolt for reasons later made apparent. The enclosed end It and the removable collar 18 have a longitudinal slot 19 so that the bolt may clear the ejector more fully described hereinafter.

The front end of the bolt is open, and is enlarged as at 20, FIGURE 5. As is most clearly shown in FIG. 7, the enlarged end 20 comprises a circular member having a vertical slot 21 therein, dividing the enlarged front end 20 into the two substantially semi-circular members 20a and 20b. The members Ztla and 20b have upper coaxial bores 22a and 22b which communicate with the slot 21, and lower coaxial bores 23a and 23b which also communicate with the slot 21.

The member 20b has a perforation 24 in the direction of the axis of the bolt. As will be clear from FIGS. 5 and 6, the perforation 24 is of enlarged diameter near the rear face of the member 20b whereby .to form a shoulder 24a. The member 20a is provided with a similar perforation 25 having a shoulder 25a. The purpose of the perforations 24 and 25 will be made apparent hereinafter.

As shown in FIG. 1, the bolt of the present invention is provided with two locking members 26 and 26a. These locking members are identical and the locking member 26 is illustrated in FIG. 3. The locking member is provided at its forward end with a downwardly depending extension 27 having a locking surface 28, and with a rearward extension 29 having an arcuate bottom surface 30 and a sloping upper cam surface 31. The remaining portion of the locking means 26 comprises an eccentric weight 32 so designed as to tend to urge the forward extension 27 downwardly by inertia. The locking means has a perforation 33 for receipt of a pivot pin. As will be evident from FIGS. 1, 2 and 7, the locking means 26 and 26a are pivotally afllxed to the members 20a and 2% within the slot 21 by pivot pins 34a and 34b passing through the transverse perforations 22a and 22b and 23a and 23b respectively.

The central hollow cylindrical portion 9 of the bolt has in its upper and lower surfaces slots 35 and 36 adapted to serve as clearance slots for the rearward extensions 29 of the locking means 26 and 26a respectively. The bolt portion 9 is also provided with an upper ejection slot 37 and a lower magazine clearance slot 38.

As will be clear from FIGS. 1 and 2, the bolt 8 is As illusadapted to telescope on the enlarged portion 4a of the barrel 4. The longitudinal slots 7 in the portion 4a of the barrel serve as clearance slots for the rearward extensions 29 on the locking means 26 and 26a.

Within the receiver 1, there is located a disc or plate 39 adapted to lie adjacent the closed end 2 of the receiver. Two parallel spaced recoil spring guide rods 40 and 41 pass through the plate 39 and are permanently aflixed to it. Ends of the rods 40 and 41 pass through perforations 42 and 43 respectively in the closed end 2 of the receiver. These perforations serve as guides for properly locating the plate 39 and rods 40 and 41 during assembly of the weapon.

As illustrated, the forward ends of the rods 40 and 41 are adapted to extend through the perforations 24 and 25 in the portions 20b and 20a respectively of the bolt. Recoil springs 44 and 45 are supported by the spring guide rods 40 and 41 respectively. The forward ends of the recoil springs abut against the shoulders 24a and 25a of the perforations 24 and 25 in the enlarged front end of the bolt, while the rear ends of the recoil springs abut against the plate 3?. Thus, the telescoping bolt may move axially with respect to the barrel, but is urged to its forward position by the recoil springs 44 and 45.

When the bolt 8 reaches its forward position and stops, the eccentric weights 32 of the locking means 26 and 26a cause the forward extensions 27 of the locking means to pivot downwardly so that the locking surfaces 28 engage the shoulder 412 on the barrel, with the result that the bolt is locked in place to the barrel.

As shown in FIGS. 1 and 2, the central cylindrical portion 9 of the bolt is provided with a hollow cylindrical weight 46 having an internal diameter such that the weight may freely slide axially of the central portion 9 between the enlarged front end 20 and the rear collar 18. As the weight moves to its forward position on the bolt, it is adapted to engage the cam surfaces 31 on the locking means 26 and 26a causing these means to pivot, disengaging the locking surfaces 28 from the shoulder 4a on the barrel.

The weapon of the present invention is provided with a trigger and sear mechanism. The trigger and sear mech anism may be of any suitable and well known type. For purposes of an exemplary showing, the trigger 47 is provided with an integral sear 48 adapted to engage the front surface of the enlarged front end 20 of the bolt. When the sear so engages the bolt, the bolt will be held in its retracted position until the trigger is pulled. Spring means 49 may be provided to retain the trigger in its unactuated position. As illustrated, the trigger is in its depressed position and it will be seen that the bolt is free to pass back and forth over the sear.

A grip 50 of any suitable type may be afiixed to the receiver 1. The grip 50 is illustrated as having a hollow central portion forming a magazine well 51. A magazine 52 containing a number of rounds 53 is shown in position within the magazine well. Again, the magazine may be of any well known and suitable type, but preferably will be a two-position magazine. The weapon will be provided with an ejector comprising an upstanding finger adapted to pass through the slot 19 in the rear end of the bolt as the bolt moves rearwardly, and eject a spent cartridge through the ejector slot 37 in the bolt and an ejector port in the receiver (not shown). The ejector 54 may be affixed to the rear end of the magazine as shown, or it may be afiixed to the insidesurface of the receiver 1.

The weapon will also be equipped with suitable means for retracting the bolt. It will be understood by one skilled in the art that the retracting means may be of any suitable and well-known type. For purposes of an exemplary showing, one form of retracting means is illustrated in dot-dash lines in FIGS. 1 and 2. The exemplary retracting means comprises an element 55 having inwardly extending fingers 56 and 57 and a retracting handle 58. The handle 58 will extend through a slot in the receiver (not shown). The fingers 56 and 57 are adapted to engage the surfaces 59 and 66 on the locking means 26 and 26a respectively. When the retracting handle is pulled rearwardly, contact of the above mentioned fingers against the above mentioned surfaces will cause the locking means 26 and 26a to pivot to an open position enabling the bolt to be pulled rearwardly. The bolt may be pulled rearwardly until engaged by the sear 48 and held thereby in its rearward position. The retracting handle will be provided with spring means (not shown) to cause it to return to its forward position.

The operation of the firearm of the present invention is as follows. A loaded magazine 52 is inserted in the magazine well 51 of the grip 50. The magazine well may be equipped with a catch means (not shown) which will securely hold the magazine in place.

The bolt is then retracted by means of the retracting handle 58. The bolt is moved thereby until it is engaged by the sear 48 and held in its retracted position. As the bolt is so retracted, the two recoil springs 44 and 45 are compressed, storing energy for the firing cycle. When the bolt is retracted, the top round in the magazine 52 extends up into the slot 38 in the bolt since, as is conventional, the magazine will be provided with a spring (not shown) tending to urge the rounds upwardly.

Upon depression of the trigger, the sear is disengaged from the bolt and the recoil springs 44 and 45 drive the bolt forwardly. The rapid forward acceleration of the bolt causes the sliding Weight 46 to slide rearwardly on the bolt until it stops against the collar 18. As the leading edge of the enlarged end 18 of the bolt comes into contact with the base of the topmost round, the round is stripped from the magazine 52, and is driven forward into the chamber of the barrel 4. The magazine may be provided with lips (not shown) which, as is conventional, direct the round into the chamber. The entrance to the barrel chamber may be funnel-shaped to assist in chambering the round at high speed. This, too, is conventional. The bolt continues in its forward movement until the base of the round contacts the bottom of the recess in the face of the bolt. At this instant the downwardly depending portion 14a of the extractor 14 snaps over the rim of the round and the fixed firing pin 12 drives into the primer of the round setting it oif.

At the instant of firing, the bolt is brought to an abrupt stop at its forwardmost position, and the eccentric weights- 32 on the locking means 26 and 26a cause them to pivot on their respective pivot pins 34a and 34b so that the locking surfaces 28 engage the shoulder 4b on the barrel. Thus, the bolt 8 is locked to the barrel 4 simultaneously with the firing of the round, preventing the bolt from being blown to the rear at the instant of highest chamber pressure. This highest chamber pressure occurs immediately after the firing of the round.

When the bolt is brought to an abrupt stop at the time of firing, the sliding weight 46 which has been moving at the same velocity as the bolt, continues its forward movement until stopped by the enlarged forward end 20 of the bolt. Just before contacting the forward end of the bolt, the sliding weight 46 engages the camming surfaces 31 of the locking means 26 and 26a. The rearward extensions 29 of the locking means are depressed into the slots 35 and 36 of the bolt and the slots 7 of the enlarged portion of the barrel 4a. This action causes the locking means 26 and 26a to pivot about the pivot pins disengaging the locking surfaces 28 from the locking shoulder 4b of the barrel.

When the locks have been cammed to an open position as described, the highest initial chamber pressure will have subsided, but sufficient pressure will remain in the chamber to blow the bolt back against the relatively weak recoil springs 44 and 45. The interval of time between the locking and the unlocking of the bolt may be adjusted to suit the ballistics of the round being used by 7 increasing or decreasing the length of the bolt or the weight 46 or both.

As the bolt continues its rearward movement, the extractor 14 retains the empty cartridge against the face of tie bolt. The rearward movement of the bolt causes the ejector 54 to pass through the slot 19 in the bolt. The ejector contacts the base of the spent cartridge and kicks it upwardly and sideways through the ejection slot 37 in the bolt and through an ejection port in the receiver (not shown). The bolt will continue its rearward movement until stopped by the compression of the recoil springs.

The plate 39 in the rear of the receiver 1, may be provided with a buffer, comprising a pad of any suitable resilient material. Such a buffer is shown at 59. While, normal-1y the rearward movement of the bolt will be stopped by the recoil springs, should the bolt be driven rea'rwardly with unusual force due to faulty ammunition or failure of the locking means 26 and 26a to function, it will be stopped by the buffer 59. When the rear- Ward movement of the bolt has been checked, the compressed recoil springs will drive the bolt forward initiating another firing cycle. The firing cycle will be repeated until either the magazine is emptied, or the trigger is released and the bolt is engaged by the sear.

Modifications may be made in the invention without departing from the spirit of it. For example, the locking means 26 and 26a may be spring loaded to the locking position instead of being provided with the weight means 32. Further, a submachine gun of the type described may be provided with a number of additional elements well known in the art. F or example, the weapon may be provided with a front grip, a safety, a cover for the ejection port in the receiver, and means for causing the weapon to operate with full or semiautomatic action. The latter may be achieved either by means of a selector switch, or a two step trigger well known in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an automatic firearm the improvement comprising a hollow receiver, a barrel afiixed to one end of said receiver, the rear end of said barrel extending within the hollow of said receiver, a hollow bolt having an open end and a closed end, said bolt capable of moving axially with respect to said rear end of said barrel to a forward and a rear position, said bolt being in telescopic relationship with said rear end of said barrel when in said forward position, means on said bolt to lock said bolt to said barrel when said bolt is in its forward position, and

inertia means slidably mounted on said bolt for disengaging said locking means from said barrel, means on said bolt for imparting movement to said inertia means when said bolt moves to said forward position, means in connection with said bolt for urging said bolt to its forward position, and a fixed firing pin in association with said bolt.

2. The structure claimed in claim 1 wherein said locking means comprises at least one element pivotally mounted on said bolt at said open end, said element having a locking and an unlocking position, means for urging said element to a locking position when the bolt is stopped at its forward position, and mean-s on said element engageable by said sliding means whereby said sliding means may cause said element to pivot to said unlocking position.

3. The structure claimed in claim 2 wherein a portion of said rear end of said barrel extending within said receiver is of increased diameter, said portion of increased diameter forming a locking shoulder on said barrel, said locking shoulder engageable by said locking means.

4. The structure claimed in claim 3 including an enlarged front end .and an enlarged rear end on said bolt, said sliding means being freely movable on said bolt between said enlarged ends.

5. The structure claimed in claim 4 wherein said enlarged front end of said bolt is provided with a transverse slot perpendicular to the axis of said bolt, said locking means comprising at least one element pivotally mounted to said enlarged front end of said bolt within said slot, said element swingable from a locking position to an unlocking position.

6. The structure claimed in claim 5 wherein said locking means comp-rises an element having a forward extension and a rear extension, said forward extension having a locking surface engageable with said locking shoulder on said barrel, said rear extension having a cam surface engageable by said sliding means whereby to cam said locking means to said unlocking position when said sliding means approaches said enlarged front end of said bolt.

7. The structure claimed in claim 6 wherein said means for causing said locking means to pivot to said locking position at the time said bolt stops at its forward position comprises a weight, said weight being an integral part of said locking means.

8. In an automatic firearm the improvement comprising a hollow receiver, a barrel afiixed to one end of said receiver, a bolt capable of moving axially with respect to said barrel within said receiver between a forward and rearward position, means on said bolt to lock said bolt in its forward position, and inertia means slidably mounted for disengaging said locking means, means on said bolt for imparting movement to said inertia means when said bolt moves to said forward position, means in connection with said bolt for urging said bolt to its forward position.

References Cited by the Examiner UNITED STATES PATENTS 739,732 9/1903 Sj0gren 89-182 1,057,329 3/1913 Clarus 89182 X 2,101,957 12/1937 Sanders 89182 BENJAMIN A. BORCHELT, Primary Examiner.

FRED C. MATTERN, IR., Examiner. 

1. IN AN AUTOMATIC FIREARM THE IMPROVEMENT COMPRISING A HOLLOW RECEIVER, A BARREL AFFIXED TO ONE END OF SAID RECEIVER, THE REAR END OF SAID BARREL EXTENDING WITHIN THE HOLLOW OF SAID RECEIVER, A HOLLOW BOLT HAVING AN OPEN END AND CLOSED END, SAID BOLT CAPABLE OF MOVING AXIALLY WITH RESPECT TO SAID REAR END OF SAID BARREL TO A FORWARD AND A REAR POSITION, SAID BOLT BEING IN TELESCOPIC RELATIONSHIP WITH SAID REAR END OF SAID BARREL WHEN IN SAID FORWARD POSITION, MEANS ON SAID BOLT TO LOCK SAID BOLT TO SAID BARREL WHEN SAID BOLT IS IN ITS FORWARD POSITION, AND INERTIA MEANS SLIDABLY MOUNTED ON SAID BOLT FOR DISENGAGING SAID LOCKING MEANS FROM SAID BARREL, MEANS ON SAID BOLT FOR IMPARTING MOVEMENT TO SAID INERTIA MEANS WHEN SAID BOLT MOVES TO SAID FORWARD POSITION, MEANS IN CONNECTION WITH SAID BOLT FOR URGING SAID BOLT TO ITS FORWARD POSITION, AND A FIXED FIRING PIN IN ASSOCIATION WITH SAID BOLT. 